Efficient Photocatalytic Carbonyl Alkylative Amination Enabled by Titanium‐Dioxide‐Mediated Decarboxylation

Abstract

Herein, a heterogeneous carbonyl alkylative amination reaction that proceeds by photoredox catalysis has been developed. The use of nano titanium dioxide (TiO2, 25 nm) as photocatalyst allows efficient synthesis of diverse amines in good to excellent yields. Mechanistic studies reveal a single‐electron‐transfer mechanism involving the photoexcitation of TiO2 to generate alkyl radicals from carboxylic acids decarboxylation. This protocol highlights the utility of using heterogeneous semiconductor photocatalysts to promote a practical and general synthesis of complex amines from readily available feedstocks.

Modular construction of N-arylated amino acid esters enabled by a photoredox-catalyzed multicomponent reaction

“…With the optimized conditions in hand, we then investigated the scope of aniline using 1 and 3 as the reaction partners. As illustrated in Table 2, both electron-withdrawing and electrondonating substituents worked well in this reaction providing N-arylated amino acid esters in moderate to excellent yields (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19). Functional groups such as methoxyl, fluoride, methyl, t-butyl, amine, OCF 3 , trifluoromethyl, ester and amide groups at the para-position of aniline were all tolerated providing the corresponding products in 68-94% yields (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15).…”

“…Anilines bearing ortho-substituents (12 and 13) or metasubstituents (14, 15, and 16) were suitable substrates producing the desired products in good yields. Moreover, the heteroaryl anilines gave the corresponding target compounds in 77%, 67% and 89% yields, respectively (17)(18)(19).…”

A direct pathway for the coupling of arenes and alkylamines via a heterogeneous zeolite-based photocatalyst

“…Therefore, heterogeneous catalysts are typically studied as promising and renewable alternatives, but they have rarely been considered for photocatalytic amination. 22,23 Faujasite type zeolites, which are aluminosilicates made up of SiO 4 and AlO 4 tetrahedra, are an appealing group of microporous, crystalline materials with a three-dimensional framework structure connected by interlinked voids. 24 These zeolite materials are currently applied in large-scale industrial processes (e.g.…”

“…Therefore, heterogeneous catalysts are typically studied as promising and renewable alternatives, but they have rarely been considered for photocatalytic amination. 22,23…”

Photo-driven metal-free multicomponent reaction between aldehydes, anilines and 4-substituted-DHPs for the synthesis of secondary amines

“…Photoredox catalysis continues to be a vibrant research area in the synthetic community due to the obvious advantages of high efficiency, versatility, mild reaction conditions, energy savings and operational simplicity. 6 In this regard, considerable efforts have been focused on photocatalyzed free-radical transformations of imines and iminiums in recent years, 7,8 in which protocols involving the functionalization of aldimines generated in situ from aldehydes and amines have been actively pursued for the step-economical synthesis of secondary amines. 8 d,h , i , n , q , r , t , u , w , x , y Notably, motivated by the advantages of multicomponent reactions, 9 Molander and co-workers first realized the visible-light photoredox-catalyzed three-component reactions for the preparation of various secondary amines through the addition of alkyl radicals from alkyltrifluoroborates to aldimines formed in situ from aldehydes and anilines (Scheme 1a, path A).…”